''Butyriboletus appendiculatus'' is an edible pored mushroom that grows under

oak An oak is a tree or shrub in the genus ''Quercus'' (; Latin "oak tree") of the beech family, Fagaceae. There are approximately 500 extant species of oaks. The common name "oak" also appears in the names of species in related genera, notably ''L ...

s and other broad leaved trees such as

beech Beech (''Fagus'') is a genus of deciduous trees in the family Fagaceae, native to temperate Europe, Asia, and North America. Recent classifications recognize 10 to 13 species in two distinct subgenera, ''Engleriana'' and ''Fagus''. The ''Engle ...

. It is commonly known as the butter bolete. It often grows in large colonies beneath the oak trees, and is frequently found cohabiting with old oaks in ancient woodland. It is relatively rare in Britain. Its stipe and pores are often bright yellow (hence its name of butter bolete) and its flesh stains bright blue when cut or bruised.

Taxonomy

The species was first described scientifically by German polymath

Jacob Christian Schäffer Jacob Christian Schäffer, alternatively Jakob, (31 May 1718 – 5 January 1790) was a German dean, professor, botanist, mycologist, entomologist, ornithologist and inventor. Biography From 1736 to 1738 he studied Theology at the University of ...

in 1774 as ''Boletus appendiculatus''. American

Charles Horton Peck Charles Horton Peck (March 30, 1833 – July 11, 1917) was an American mycologist of the 19th and early 20th centuries. He was the New York State Botanist from 1867 to 1915, a period in which he described over 2,700 species of North American fun ...

later used the name in 1896 for a species he found in

Washington Washington commonly refers to: * Washington (state), United States * Washington, D.C., the capital of the United States ** A metonym for the federal government of the United States ** Washington metropolitan area, the metropolitan area centered on ...

, but the name was illegitimate because Schäffer's earlier usage has priority. Until 2014, it was classified in the genus '' Boletus''.

Molecular A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and bioche ...

phylogenetic analysis demonstrated that it and other members of ''Boletus'' section ''Appendiculati'' were

phylogenetic In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...

ally distinct from ''Boletus'', and the genus ''

Butyriboletus ''Butyriboletus'' is a genus of fungi in the family Boletaceae. The genus was circumscribed in 2014 by mycologists David Arora and Jonathan L. Frank to accommodate "butter bolete" species that were shown by molecular phylogenetics, molecular anal ...

'' was created to contain them. The

specific epithet In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...

''appendiculatus'' means "with a small appendage".

Description

Fruit bodies The sporocarp (also known as fruiting body, fruit body or fruitbody) of fungi is a multicellular structure on which spore-producing structures, such as basidia or asci, are borne. The fruitbody is part of the sexual phase of a fungal life cyc ...

of ''Butyriboletus appendiculatus'' have convex to flattened, brown to yellowish brown caps measuring in diameter. They have a dry to slightly sticky surface texture that may develop cracks with age. The mushroom has very firm yellowish flesh that may slowly change blue when cut or bruised. The pores on the cap undersurface are butter yellow, and may also bruise blue, although this is less likely in young specimens. The stipe is long by thick at the top near the attachment to the cap, and ranges from thicker at the base to equal throughout, to tapered at the bottom. It is also yellow, sometimes developing brownish to reddish stains, and may have fine reticulations near the top. The spore print is dark olive-brown. Individual spores are ellipsoidal to spindle-shaped, smooth, and measure 12–15 by 3.5–5

µm The micrometre ( international spelling as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer (American spelling), also commonly known as a micron, is a unit of length in the International System of Unit ...

Similar species

The Europe species ''

Butyriboletus subappendiculatus ''Butyriboletus subappendiculatus'' is a pored mushroom in the family Boletaceae. This European species was originally described as a species of '' Boletus'' in 1979, but later transferred to ''Butyriboletus'' in 2014. It is considered endanger ...

'' is quite similar to ''B. appendiculatus'' in microscopic characters. It can be distinguished in the field by the lack of a bruising color reaction, more pallid cap colors, and growth under

conifer Conifers are a group of conifer cone, cone-bearing Spermatophyte, seed plants, a subset of gymnosperms. Scientifically, they make up the phylum, division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a single ...

s. Also similar are ''

Butyriboletus regius ''Butyriboletus regius'' (formerly ''Boletus regius''), commonly known as the royal bolete or red-capped butter bolete, is a basidiomycete fungus of the genus '' Boletus'' found in China and Europe. ''B. regius'' has a pink cap, yellow fl ...

'' and '' Boletus edulis''.

Edibility

The bolete is

edible An edible item is any item that is safe for humans to eat. "Edible" is differentiated from "eatable" because it does not indicate how an item tastes, only whether it is fit to be eaten. Nonpoisonous items found in nature – such as some mushroo ...

and considered choice by several sources, although some warn that certain individuals may have an allergic reaction to it. The earthy flavor of the mushrooms make them suitable for soups, sauces and stews. Cooked portions will often turn blue, then gray, then return to their original yellow color.

Distribution and habitat

''Butyriboletus appendiculatus'' is found in Europe and North America. Fruit bodies grow singly, scattered, or in groups under

hardwood Hardwood is wood from dicot trees. These are usually found in broad-leaved temperate and tropical forests. In temperate and boreal latitudes they are mostly deciduous, but in tropics and subtropics mostly evergreen. Hardwood (which comes from ...

trees. In North America, it is more common in the

Pacific Northwest The Pacific Northwest (sometimes Cascadia, or simply abbreviated as PNW) is a geographic region in western North America bounded by its coastal waters of the Pacific Ocean to the west and, loosely, by the Rocky Mountains to the east. Though ...

region, where it often associates with live oak and tanoak.

References